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US 5,856,074 AGranted
Fixing bath
AssigneeAgfa-Gevaert
InventorsGustav Tappe, Norman Klaunzer
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AssigneeAgfa-Gevaert
InventorsGustav Tappe, Norman Klaunzer
Estimating the term…
This invention relates to a fixing bath containing a biologically degradable complexing agent of formula I ##STR1## wherein R.sup.1-4 represents hydrogen, C.sub.1 -C.sub.10 -alkyl, hydroxy-C.sub.1 -C.sub.10 -alkyl, C.sub.1 -C.sub.10 -alkoxy-C.sub.1 -C.sub.10 -alkyl, carboxy-C.sub.2 -C.sub.10 -alkyl, dicarboxy-C.sub.1 -C.sub.10 -alkyl, carboxy-hydroxy-C.sub.1 -C.sub.10 -alkyl, hydroxy-C.sub.1 -C.sub.5 -alkyl-(oxy-C.sub.1 -C.sub.5 -alkyl).sub.n, or C.sub.1 -C.sub.5 -alkoxy-C.sub.1 -C.sub.5 -alkyl-(oxy-C.sub.1 -C.sub.5 -alkyl).sub.n, M represents hydrogen, lithium, sodium, potassium or ammonium, and n represents 1, 2, 3 or 4, the iron(III) complex salt of which does not impede electrolytic desilverisation during the regeneration of spent fixing bath.
A fixing bath which comprises active ingredients and auxiliary materials for the fixing process, and additionally contains a complexing agent of formula I ##STR4## wherein R.sup.1-4 independently of one another represent hydrogen, C.sub.1 -C.sub.10 -alkyl, hydroxy-C.sub.1 -C.sub.10 -alkyl, C.sub.1 -C.sub.10 -alkoxy-C.sub.1 -C.sub.10 -alkyl, carboxy-C.sub.2 -C.sub.10 -alkyl, dicarboxy-C.sub.1 -C.sub.10 -alkyl, carboxy-hydroxy-C.sub.1 -C.sub.10 -alkyl, hydroxy-C.sub.1 -C.sub.5 -alkyl-(oxy-C.sub.1 -C.sub.5 -alkyl).sub.n, or C.sub.1 -C.sub.5 -alkoxy-C.sub.1 -C.sub.5 -alkyl-(oxy-C.sub.1 -C.sub.5 -alkyl).sub.n,
Dependencies are inferred from the claim text.
No related US applications are recorded in the indexed filing history.
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Colour processes using colour-coupling substances; Materials therefor; Preparing or processing such materials: bleach-fixing or agents therefor ;…
Having nitrogen and oxygen atoms as the only ring hetero atoms: six-membered rings
Processes using silver-salt-containing photosensitive materials or agents therefor: fixing; Developing-fixing; Hardening-fixing
Photosensitive materials for photographic purposes
Term ended 17 Oct 2017 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
This invention relates to a fixing bath which is suitable for the treatment of photographic silver halide materials and which contains a biologically degradable complexing agent as a lime-preventing agent which masks iron(III) complex salts dragged in by the treatment process. The iron(III) ions thereby lose their oxidising capacity and problems during the electrolytic regeneration of spent fixing bath are avoided.
Sodium or ammonium thiosulphate is predominantly used for fixing. These fixing baths, the pH of which is in the slightly acidic to slightly alkaline range, are usually provided with ethylenediaminetetraacetic acid (EDTA) or nitrilotriacetic acid (NTA) as a lime-preventing agent. Prior art fixing baths are described in U.S. Pat. No. 4,444,873 and EP-A-486 909, for example.
Spent fixing baths contain considerable amounts of dissolved silver. This silver can be recovered, by electrolysis for example. Spent fixing baths are collected for desilverisation; desilverisation in a closed cycle is also possible for modern developing machines which are operated continuously. Corresponding methods are described in J.Appl.Photogr. Engineering 2 (176) 36 and in J. Imaging Techn. 11 (1985) 43.
A fixing bath of the following composition, which had an accurately defined concentration of calcium ions, was prepared and treated with various complexing agents in different concentrations (Table 1). All the fixing baths according to the invention exhibited no precipitation during the period of observation of 120 days. The fixing baths were stored in open vessels at room temperature. A decrease in volume due to evaporation was compensated for by periodically topping up the baths with deionised water.
______________________________________ Fixing bath: ______________________________________ water (deionised) 800 ml sodium sulphate 10 g sodium sulphite 20 g sodium thiosulphate 60 g calcium chloride solution (80 g/l) 5 ml complexing agent see Table 1 ______________________________________
The pH was adjusted to 7 and the baths were made up to 1 liter with deionised water.